Re: [TCML] microbrute DRSSTC

[W5als <w5als@xxxxxxxxx>]

Hi Joe
     I found my first problem, the primary wires were backwards. I switch them it
Fire off, I brought it up twice and the over current did what should have since
R25 is set at .70 volts. I turn it up to 3.2 volts it came on for 3-4 seconds and
Went off would not work any more. I than check the IGBT's and one had shorted
have no idea why that happen.
Thanks
Alton

Sent from my iPad

On Jan 1, 2013, at 6:24 PM, Joe Mastroianni <joe@xxxxxxxxxxxxxx> wrote:

> 
> 
> Hi Alton,
> Well, if everything was working correctly and you just weren't triggering the IGBTs, you'd at least get a little current draw that would be charging up the DC caps in the DC supply, but then that would probably tail off as well.  So, the whole thing may stem as a problem that you're not triggering the IGBTs, even though the circuit is buzzing away with the gate triggering signal.
> 
> OR - it could be that for some reason you're not actually charging up the DC supply.  Your HV diodes could be blown up (but probably not).   (Very carefully) Check the voltage across C41 (you could also do this at any other number of places)  to make sure you're actually getting a tank supply. If not, and you have no current draw at all from your variac, then something is just plain not connected (or a trace is broken on the PCB, or your 5A fuse is blown, or CR43 and CR44 are blown up...but I doubt it).
> 
> If you do have a good DC supply on the tank circuit, then you're just not triggering the IGBTs.  That could be lots of things...like your VRxx protection diodes are screwy but also unlikely, or more likely, your GDT is wound wrong.  That would be very easy to get wrong.  Look at the output on a scope and make sure you've got good pulses coming off there to the gate of each IGBT and make sure they're correctly phased.  If they're not phased right, you're going to know right away because things would smoke.  Both IGBTS on at the same time can become a cause to run in bigger coils..;)
> 
> Or -the pulses from your interrupter may just be too short...  Gotta check that with a scope.  I think the maximum pulse width he suggests is 200ns, but my memory is very bad, and it is possible to have such a short pulse width that nothing happens.
> 
> Good luck with your debugging,
> 
> Joe
> 
> 
>>>>> 
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>> HI Joe
>>      I have reverse the wire through the current transformer did not help. the one strange thing
>> is on the 5amp fuse side it pull no current at all through my variac with a current  meter on it.
>> I have also tried tuning it too never pull current or get a arc. I still think something in or around
>> the IGBT's is just not right.
>> alton
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